Fantasy novel by Richard Adams which tells the story of fiver hazel bigwig and silver?

The novel you're referring to is "Watership Down" by Richard Adams. The story follows a group of rabbits as they leave their warren and embark on a journey to find a new home. The main characters include Fiver, Hazel, Bigwig, and Silver. Fiver is a sensitive rabbit with the power to see visions of the future, while Hazel is the intelligent and compassionate leader of the group. Bigwig is a strong and brave warrior, and Silver is a cunning and resourceful rabbit. Together, they face many challenges and dangers as they search for a safe place to live.